In recent years, dispersed microdroplet liquid crystal systems have been developed. In a dispersed microdroplet liquid crystal system, a liquid crystal material and a liquid polymer precursor are mixed together and then the mixture cast into a film. The polymer precursor material which constitutes the matrix of the film is allowed to react and to cure. The resulting product is a polymeric film that contains dispersed therein many small droplets (also called microdroplets) of liquid crystal material. The nature of the liquid crystal material and the temperature of the film determine the light transparency of the film. It may be opaque or transparent at room temperature. The liquid crystal film used in the present invention is opaque at room temperature. When the film is heated, the heated portions of the film become transparent.
Liquid crystal films previously made by the dispersion technique do not have memory, i.e., they revert to their scattering (or opaque) state as soon as the voltage is removed in the case of nematic materials or the temperature is decreased in general. In many applications, it is desirable for the liquid crystal film to have memory such that the occurrence of a specific event may be recorded. For instance, in large area windows using these films to control light transmittance, the power consumption could be reduced if the film had memory since power could be removed once the film has been converted to its transparent state. Memory would also be an important safety feature in such an application since a window would remain transparent in the event of a power failure. Memory can also be used to simplify addressing in liquid crystal displays in large areas. The word addressing is commonly used to describe the process of converting a specific portion of a liquid crystal from one optical state to another optical state. Furthermore, memory effect is essential in the construction of a liquid crystal device to record maximum temperatures.
It is therefore an object of the present invention to provide a method of creating memory in an optically responsive film by using liquid crystal microdroplets having molecules arranged in a smectic structure dispersed in a polymeric film.
It is another object of the present invention to provide a method of creating memory effect in an optically responsive film by using liquid crystal microdroplets having molecules arranged in a smectic structure dispersed in a polymeric film which can be performed in a convenient and economical way.